1. Field of the Invention
This invention generally relates to a rotary rolling contact bearing assembly, and, in particular, to a lubricatable rotary bearing assembly including a plurality of rolling members interposed between a pair of inner and outer rings.
2. Description of the Prior Art
A rotary crossed roller type rolling contact bearing assembly is disclosed in the Japanese Utility Model Post-examination Publication No. 62-16495, which was published for the purpose of oppositions on Apr. 25, 1987 and assigned to the Assignee of this application and which is hereby incorporated by reference. Such a rotary motion rolling contact bearing assembly generally includes a plurality of rolling members interposed between a pair of inner and outer rings which rotate relative to each other. The rolling contact members may be cylindrical or truncated conical rollers or balls. In the case of rollers, they are provided in a crossed arrangement, i.e., any two adjacent rollers being oriented with their rotating axes extending perpendicular to each other when viewed in the direction of advancement of the rollers.
A rotary rolling contact bearing assembly shown in the above-identified Utility Model Publication includes an insertion hole provided in either of the inner and outer rings, through which rolling members may be inserted into an annular path defined between the inner and outer rings. A closure member is fitted into the insertion hole after insertion of rolling members into the annular path to close the insertion hole to thereby prevent the rolling members from falling off. The rotary contact bearing assembly shown in the above-identified Utility Model Publication is advantageous in many respects, for example compactness, easiness in manufacture and rigidness in structure; however, difficulty is encountered in lubrication of the bearing assembly. That is, it is not easy to provide oil and/or grease particularly to the annular rolling contact path of the bearing assembly. Lubrication may not be a problem in some applications, but lubrication becomes critical in other applications. Therefore, the scope of application of the rotary rolling contact bearing assembly shown in the above-identified Utility Model Publication was rather limited. In particular, such rotary rolling contact bearing assemblies find a usage in robots, e.g., joints of their arms, or they may be required to support a rotating shaft at high speed. In these cases, the rotary bearing assemblies must be lubricated to maintain its high performance. The above-identified Utility Model Publication is totally silent as to the problem of lubrication.